#include <stdio.h>
#include <stdlib.h>
int main()
{
    int p,d,m,s,i;
    scanf("%d%d%d%d",&p,&d,&m,&s);
    int ml=s;
    for(i=0;;)
    {
        if(p<=m)
            p=m;
        ml=ml-p;
        if(ml>=0)
            i++;
        else
        break;
          p=p-d;

    }
    printf("%d",i);
}